From 959cbe93cdc3c0f7a3e8340c86f53db488e25aa1 Mon Sep 17 00:00:00 2001
From: Brian Norris <banorris@uci.edu>
Date: Fri, 2 Nov 2012 18:41:30 -0700
Subject: [PATCH 1/1] linuxrwlocks: add linux locks test

---
 Makefile                    |   2 +-
 linuxrwlocks/.gitignore     |   1 +
 linuxrwlocks/Makefile       |  11 ++++
 linuxrwlocks/linuxrwlocks.c | 112 ++++++++++++++++++++++++++++++++++++
 4 files changed, 125 insertions(+), 1 deletion(-)
 create mode 100644 linuxrwlocks/.gitignore
 create mode 100644 linuxrwlocks/Makefile
 create mode 100644 linuxrwlocks/linuxrwlocks.c

diff --git a/Makefile b/Makefile
index e5ff6cc..9e102ec 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-DIRS := barrier mcs-lock mpmc-queue spsc-queue
+DIRS := barrier mcs-lock mpmc-queue spsc-queue linuxrwlocks
 
 .PHONY: $(DIRS)
 
diff --git a/linuxrwlocks/.gitignore b/linuxrwlocks/.gitignore
new file mode 100644
index 0000000..2fdb632
--- /dev/null
+++ b/linuxrwlocks/.gitignore
@@ -0,0 +1 @@
+/linuxrwlocks
diff --git a/linuxrwlocks/Makefile b/linuxrwlocks/Makefile
new file mode 100644
index 0000000..d66ada3
--- /dev/null
+++ b/linuxrwlocks/Makefile
@@ -0,0 +1,11 @@
+include ../benchmarks.mk
+
+TESTNAME = linuxrwlocks
+
+all: $(TESTNAME)
+
+$(TESTNAME): $(TESTNAME).c
+	$(CC) -o $@ $< $(CPPFLAGS) $(LDFLAGS)
+
+clean:
+	rm -f $(TESTNAME) *.o
diff --git a/linuxrwlocks/linuxrwlocks.c b/linuxrwlocks/linuxrwlocks.c
new file mode 100644
index 0000000..7e317aa
--- /dev/null
+++ b/linuxrwlocks/linuxrwlocks.c
@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <threads.h>
+#include <stdatomic.h>
+
+#include "librace.h"
+
+#define RW_LOCK_BIAS            0x00100000
+#define WRITE_LOCK_CMP          RW_LOCK_BIAS
+
+/** Example implementation of linux rw lock along with 2 thread test
+ *  driver... */
+
+typedef union {
+	atomic_int lock;
+} rwlock_t;
+
+static inline int read_can_lock(rwlock_t *lock)
+{
+	return atomic_load_explicit(&lock->lock, memory_order_relaxed) > 0;
+}
+
+static inline int write_can_lock(rwlock_t *lock)
+{
+	return atomic_load_explicit(&lock->lock, memory_order_relaxed) == RW_LOCK_BIAS;
+}
+
+static inline void read_lock(rwlock_t *rw)
+{
+	int priorvalue = atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
+	while (priorvalue <= 0) {
+		atomic_fetch_add_explicit(&rw->lock, 1, memory_order_relaxed);
+		do {
+			priorvalue = atomic_load_explicit(&rw->lock, memory_order_relaxed);
+		} while (priorvalue <= 0);
+		priorvalue = atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
+	}
+}
+
+static inline void write_lock(rwlock_t *rw)
+{
+	int priorvalue = atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
+	while (priorvalue != RW_LOCK_BIAS) {
+		atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_relaxed);
+		do {
+			priorvalue = atomic_load_explicit(&rw->lock, memory_order_relaxed);
+		} while (priorvalue != RW_LOCK_BIAS);
+		priorvalue = atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
+	}
+}
+
+static inline int read_trylock(rwlock_t *rw)
+{
+	int priorvalue = atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
+	if (priorvalue > 0)
+		return 1;
+
+	atomic_fetch_add_explicit(&rw->lock, 1, memory_order_relaxed);
+	return 0;
+}
+
+static inline int write_trylock(rwlock_t *rw)
+{
+	int priorvalue = atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
+	if (priorvalue == RW_LOCK_BIAS)
+		return 1;
+
+	atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_relaxed);
+	return 0;
+}
+
+static inline void read_unlock(rwlock_t *rw)
+{
+	atomic_fetch_add_explicit(&rw->lock, 1, memory_order_release);
+}
+
+static inline void write_unlock(rwlock_t *rw)
+{
+	atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_release);
+}
+
+rwlock_t mylock;
+int shareddata;
+
+static void a(void *obj)
+{
+	int i;
+	for(i = 0; i < 2; i++) {
+		if ((i % 2) == 0) {
+			read_lock(&mylock);
+			load_32(&shareddata);
+			read_unlock(&mylock);
+		} else {
+			write_lock(&mylock);
+			store_32(&shareddata,(unsigned int)i);
+			write_unlock(&mylock);
+		}
+	}
+}
+
+int user_main(int argc, char **argv)
+{
+	thrd_t t1, t2;
+	atomic_init(&mylock.lock, RW_LOCK_BIAS);
+
+	thrd_create(&t1, (thrd_start_t)&a, NULL);
+	thrd_create(&t2, (thrd_start_t)&a, NULL);
+
+	thrd_join(t1);
+	thrd_join(t2);
+
+	return 0;
+}
-- 
2.34.1